Draft producing apparatus



July 4, 1939.

G. A. MERKT DRAFT PRODUCING APPARATUS Filed Oct. 25, 1937 2 Sheets-Sheet1 FIG. 1

/NVENTOR GUSTAV A. MERKT ATTORNE July 4, 1939. e. A. MERKT 2,164,880

01mm PRODUCING APPARATUS Filed 001;. 25, 1937 2 Sheets-Sheet 2 INVENTORCiusTAv A. MERKT A TTORNEY Patented July 4, 1939 UNITED STATES PATENTOFFICE Morgan Construction Company,

Worcester,

Mass, a corporation of Massachusetts Application October 25, 1937,Serial No. 170,901

9 Claims.

This invention relates to draft producing apparatus, and moreparticularly to the construction of ejector stacks arranged to utilize amotive fluid, such as air under pressure, for the entrainment anddischarge of another fluid, such as the waste gaseous products ofcombustion from a furnace or the like.

In one form of ejector stack heretofore proposed the .air is deliveredinto the bottom of the stack in the form of an upwardly convergingannular jet which serves to draw the waste gases upwardly through a. gaspassage beneath and coaxial with the stack. These gases are frequentlyat a high temperature, and they have caused serious damage to thevarious metal parts and greatly shortened the life of the apparatus.Moreover, some parts are heated to a greater ex tent than others, andthe resultant unequal expansion has resultedin distortion, reducing theefiicienoy and causing the operation to be generally unsatisfactory.Further difiiculties have been caused by the corrosiveaction of rainWater and condensed moisture on the metal parts.

It is accordingly one object of the invention to overcome thesedifficulties and to provide an ejector stack capable of handling hightemperature gases without damage or distortion. 1

It is a further object of the invention to provide an ejector stack soconstructed and arranged as to reduce to a minimumthe corrosion causedby rain water and condensed moisture.

With these and other objects in view, as will be apparent to thoseskilled in the art, the inven tion resides in the combination ofpartsset forth in the specification and covered by the claims appendedhereto. v

In accordance with the invention in itspre: ferred form, an expansionjoint is provided between the inlet end or throat of the stack and theassociated air nozzle, the air nozzle being secured to the gas nozzle incoaxial relation therewith. The inlet portion of the stack is surroundedby a easing into which the air is delivered and from which it flows intothe air nozzle. The air flows over the outer surface of the stack tocool the same, and, to enhance this flow, openings may be provided inthe casing through-which a part of the air may escape to atmosphere. Thethroat of the stack is preferably made slightly smaller than the gasnozzle so that rain water which enters the stack will flow into the gasflue rather than into the casing. A drain may be connected to the casingto prevent accumulation of condensed moisture therein.

Cal

Referring to the drawings illustrating one embodiment of the inventionand in which like reference numerals indicate like parts,

Fig. 1 is a vertical section through a draft producing apparatus;

Fig. 2 is a section on the line 2--2 of Fig. 1; and

Fig. 3 is' a View similar to Fig. 1 showing a slight modification.

The embodiment illustrated in Fig. 1 comprises a vertical flue itthrough which the hot gaseous products of combustion may escape from afurnace (not shown). On the top of the flue Hi there is mounted anupwardly converging frusto-conical gas nozzle H. A stack 12 is arrangedabove the gas nozzle in coaxial relation therewith, these parts beingslightly spaced apart so that air may be delivered to the stack for thepurpose of entraining the hot gases and discharging them to theatmosphere. The stack l2 comprises a cylindrical portion or throat id atits lower end, and an upwardly and outwardly flaring diffuser section l5which extends from the throat to the top of the stack. The throat M hasa slightly smaller internal diameter than the top of the gas nozzle l I,and the lower end of the throat is beve.ed at Hi to form a sharp inneredge, so that any rain water which may enter the stack will pass throughthe gas nozzle and into the flue I0 where it can do no harm.

The lower portion of the stack [2 is surrounded by a casing l3 whichrests upon the flue ID. This casing is generally cylindrical in form andhas an upwardly and inwardly sloping upper wall l9 which is secured tothe stack. This construction provides a plenum chamber 20 to which airis delivered under pressure from a suitable fan or other means (notshown) through a duct 2 I, this duct leading to one side of the casing8. The chamber 23 surrounds the adjacent inlet portion of the stack 12and overlaps the outer surface thereof for a substantial distance in thedirection of flow through the stack.

In order to direct the air from the chamber 20 into the stack forentrainment of the gases, there isprovided an upwardly convergingfrusto-conical air nozzle 23 which is mounted on the gas nozzle H insurrounding coaxial relation there- .to. The air nozzle 23 is shownprovided on its inner surface with spaced lugs 24 which may be welded atassembly to the outer surface of the gas nozzle. The conical angle ofthe air nozzle is preferably somewhat larger than that of the gas nozzleso that the annular space between these parts converges upwardly.Furthermore, the angle of the air nozzle is such, in relationship 2uessed to the sharp lower edge of the throat l4, that the air streamwill not impinge upon this edge. This construction avoids the formationof undesirable eddy currents at the entrance of the throat.

An expansion joint is provided between the lower end of the stack l2 andthe air nozzle 23 so that undue stresses and distortion of the structurewith changing temperature conditions may be avoided. For this purposethe air nozzle 23 is formed at its upper end with a cylindricalextension 25 slightly larger in diameter than the lower end of the stackand overlapping this lower end slightly in surrounding relation thereto.A sleeve 21 is welded or otherwise secured to the outside of the stackl2 a short distance above the upper end of the extension 25, this sleeveand the extension having equal outside diameters. A ring 28 of asuitable packing material overlaps both the sleeve 2'1 and the extension25 to seal the joint between these parts. This ring is held in place bymeans of a clamping ring 29 formed in arcuate sections, each sectionhaving at its ends outwardly extending apertured lugs 3|. The opposinglugs of the respective ring sections are connected by means of bolts 32.In order to prevent the packing ring 28 and the clamping ring 29 frommoving out of position axially, there is provided an outwardlyprojecting flange 34 On the stack l2 above these rings, and a similaroutwardly projecting flange 35 on the extension 25 below the rings.These flanges may be welded in position and they are spaced apart adistance somewhat exceeding the width of the packing ring 28 so thatthere will be ample room for the throat M to expand in a downwarddirection without interference.

When the air inlet duct 21 enters the casing I8 some distance below theupper wall I9 thereof, as in the embodiment illustrated, this tends toform a dead air pocket in the upper part of the chamber 28, and theadjacent portion of the stack may not be cooled to the desired extent.In order to avoid this difficulty, I preferably provide openings 31' inthe upper wall l9 near its junction with the stack, and I mount afrusto-conical hood 38 on the stack to overlie these openings andprevent rain water from passing through them. While the apparatus is inoperation, a portion of the air supplied to the chamber 20 will escapeto the atmosphere through the openings 3?, and the resultant flowthrough the upper portion of the chamber will ensure adequate cooling ofthe stack.

Under certain conditions of temperature and humidity, moisture maycondense from the air which is supplied to the chamber 20, and if thismoisture is allowed to remain in contact with the metal surfaces it maycause corrosion thereof. I accordingly prefer to provide a suitabledrain pipe as which extends from the bottom of the chamber 2! downwardlyand outwardly through the wall of the flue It. This pipe is preferablyof small size, to minimize the flow of air outwardly therethrough, andsuch air flow as does occur will aid in keeping the pipe clear.

In Fig. 3 there is illustrated a slight modification in which the casingI8 is arranged with its lower portion extending downwardly into the flueHi. This arrangement will lower the structure by several feet, and isparticularly suitable when the apparatus is to be applied to an existingflue of considerable height.

The operation of the invention will now be apparent from the abovedisclosure. Air is delivered under pressure to the plenum chamber 20 bythe duct 2| and after flowing downwardly through the chamber it passesupwardly at high velocity through the nozzle 23 and enters the throat Min the form of an upwardly converging annular jet. This jet entrains andWithdraws hot gases from the flue I0, and discharges them upwardly tothe atmosphere through the diffiuser section IS. The heat from the gasescauses the lower portion of the stack to expand downwardly, but thisexpansion causes no great stressing or distortion of the structure sincethe lower end of the stack is free to slide axially in the packing 28.The air nozzle 23 is secured directly to the gas nozzle H, so that theseparts are maintained in the desired coaxial relationship. Excessiveheating of the stack is prevented by the cooling action of the airflowing through the chamber 20, the holes 31 allowing a slight leakageto maintain a flow in the upper portion of the chamber. Rain water whichmay flow downwardly along the inner surface of the stack will drop fromthe sharp lower edge of the stack through the gas nozzle II into theflue It. Any water which may collect in the chamber 20 by reason ofcondensation can escape through the drain 40.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. Draft producing apparatus comprising a nozzle for hot gases, a stackin alignment with the nozzle, an air nozzle surrounding the gas nozzlein spaced relation thereto to direct a jet of air into the adjacent endof the stack and thus entrain the hot gases from the gas nozzle anddischarge them through the stack, a casing forming a chamber whichcommunicates with the air nozzle, the chamber surrounding the adjacentinlet portion of the stack and overlapping the outer surface thereof fora substantial distance in the direction of flow through the stack, andmeans to deliver air under pressure to the chamber and produce a flow ofair therethrough in Cooling contact with the outer surface of the saidadjacent inlet portion of the stack.

2. Draft producing apparatus comprising an upwardly directed nozzle forhot gases, an upright stack above and in vertical alignment with thenozzle, an air nozzle surrounding the gas nozzle in spaced relationthereto to direct a jet of air upwardly into the lower end of the stackand thus entrain the hot gases from the gas nozzle and discharge themupwardly through the stack, a casing forming a chamber whichcommunicates with the air nozzle and surrounds the lower portion of thestack, and means to supply air under pressure to the chamber, the casinghaving an opening near the top thereof through which a part of the aircan escape, thereby maintaining a flow of air through the chamber incooling contact with the outer surface of the lower portion of thestack. l

3. Draft producing apparatus comprising an upwardly directed nozzle forhot gases, an upright stack above and in vertical alignment with thenozzle,an air nozzle surrounding the gas nozzle in spaced relationthereto to direct a jet of air upwardly into the lower end of the stackand thus entrain the hot gases from the gas nozzle and discharge themupwardly through the stack, a casing forming a chamber whichcommunicates with the air nozzle and surrounds the lower portion of thestack, means to supply air under pressure to the chamber, the casinghaving an opening in its upper wall through which a part of the air 55can escape, thereby maintaining a flow of air through the chamber incooling contact with the the nozzle, the lower end of the stack beingsomewhat smaller than the upper end of the nozzle so that rain waterwhich enters the stack will drop into the nozzle, and means to direct ajet of air upwardly into the lower end of the stack and thus entrain thehot gases from the nozzle and discharge them upwardly through the stack.

5. Draft producing apparatus comprising an upwardly directed nozzle forhot gases, an upright stack above and in vertical alignment with thenozzle, the lower end of the stack being somewhat smaller than the upperend of the nozzle and the said lower end being beveled to form a sharpinner edge from which rain water which enters the stack will drop intothe nozzle, and means to direct a jet of air upwardly into the lower endof the stack and thus entrain the hot gases from the nozzle anddischarge them upwardly through the stack.

6. Draft producing apparatus comprising an upwardly directed nozzle forhot gases, an upright stack above and in vertical alignment with thenozzle, the lower end of the stack having a somewhat smaller diameterthan the upper end of the nozzle so that rain water which enters thestack will drop into the nozzle, an upwardly converging frusto-conicalair nozzle surrounding the gas nozzle in spaced relation thereto todirect a jet of air upwardly into the lower end of the stack and thusentrain the hot gases from the gas nozzle and discharge them upwardlythrough the stack, and a substantially cylindrical extension projectingupwardly from the air nozzle in surrounding relation to the lower end ofthe stack.

7. Draft producing apparatus comprising a nozzle for hot gases, a stackin alignment with the nozzle, a casing forming a chamber surrounding thenozzle and the adjacent inlet portion of the stack and overlapping theouter surface of the said inlet portion for a substantial distance inthe direction of flow through the stack, means to deliver air underpressure to the chamber, an air nozzle located within the chamber andsecured to the gas nozzle in surrounding relation thereto, the airnozzle being arranged to direct air from the chamber into the stack andthusentrain the hot gases and discharge them through the stack, andmeans providing a sealed expansion joint between the air nozzle and theadjacent end of the stack.

8. Draft producing apparatus comprising a nozzle for hot gases, a stackhaving a substantially cylindrical end portion in alignment with thenozzle, a casing forming a chamber surrounding the nozzle and theadjacent portion of the stack, means to deliver air under pressure tothe chamber, a frusto-conical air nozzle secured to the gas nozzle insurrounding relation thereto and arranged to direct air from the chamberinto the stack and thus entrain the hot gases and discharge them throughthe stack, and asubstantially cylindrical extension projecting from theair nozzle in surrounding relation to the adjacent end of the stack, thestack being free to slide axially within the extension as a result ofexpansion by heat.

9. Draft producing apparatus comprising a nozzle for hot gases, a stackhaving a cylindrical end portion in alignment with the nozzle, a casingforming a chamber surrounding the nozzle and the adjacent portion of thestack, means to deliver air under pressure to the chamber, afrusto-conical air nozzle secured to the gas nozzle in surroundingrelation thereto and arranged to direct air fro-m the chamber into thestack and thus entrain the hot gases and discharge them through thestack, a cylindrical extension projecting from the air nozzle insurrounding relation to the adjacent end of the stack, a cylindricalsleeve fixed to the stack and slightly spaced from the end of theextension, the sleeve and the extension having equal outside diameters,and a ring of packing material overlapping both the sleeve and theextension to seal the joint between these parts while allowing axialmovement of the stack resulting from expansion by heat.

GUSTAV A. MERKT.

